1. Field of the Invention
The present invention relates to a process for producing a branched organopolysiloxane, which can be advantageously realized economically and industrially.
2. Description of the Prior Art
As a process for producing a branched organopolysiloxane, it is known to obtain a branched organopolysiloxane, for example, by heating and, mixing a mixture containing an R.sub.3 SiO.sub.0.5 unit (hereinafter referred to as an M unit) and an R.sub.2 SiO unit (hereinafter referred to as a D unit), wherein R are each an organic group bonded to the silicon atom, in the presence of a potassium silanolate to effect equilibration reaction, and subsequently by slowly adding a hydrolysis product of a silane compound containing an M unit, a D unit and an RSiO.sub.1.5 unit (hereinafter referred to as a T unit) to the reaction mixture obtained to effect equilibration again [cf. Japanese Pre-examination Patent Publication (KOKAI) No. 58-007452 (1983)].
According to the above process, it is necessary to produce in advance the hydrolysis product containing the T unit for forming a branch. This hydrolysis product is normally produced from chlorosilanes and alkoxysilanes, and the product requires a long water-washing step for removing a generated hydrochloric acid; thus the process is economically disadvantageous. Furthermore, raw materials serving as sources providing an M-, D- or T unit are charged in a reactor in a ratio so designed as to produce a branched organopolysiloxane with desired properties. However, the ratio of units in the resultant hydrolysis product is not necessarily consistent with that as originally designed, and its viscosity are unstable; specifically, for example, lot-to-lot variations in content of each unit or viscosity may be wide. Therefore, in the above process it has been difficult to produce a branched organopolysiloxane in large quantities.